This invention relates to an optically controlling apparatus.
Recently, an optically controlling technology is known whereby light emitting elements which emit light signals in response to control signals from a control signal generator and optical fibers for transmitting light signals from these light emitting elements are used. The conduction states of photosensitive elements used in a controlled circuit are controlled in accordance with the light signals, thereby controlling the operation state of this controlled circuit. The control method of this kind can be also applied to the field of the power transmission and distribution which deals with high voltages.
The use of this optically controlling technology enables the operation of the controlled circuit which operates at high voltages (e.g. hundreds of kilovolts) to be controlled by generating light signals from the light emitting elements in response to control signals at low voltages (e.g. hundreds of volts). In addition, since the control signals from a control signal generator are converted into the light signals and thereafter they are transmitted to the controlled circuit through optical fiber bundles, the control signal generator will not be affected due to the electrical noise in the controlled circuit. However, as a potential difference between the controlled circuit which is made operative at high voltages and the control circuit which is made operative at low voltages increases, leakage currents flow through the optical fiber bundles for optically coupling the light emitting elements and the photosensitive elements, so that there is a possibility in that these currents damage the light emitting elements. That is, both ends of the optical fiber bundles are arranged near or in abutment with the light emitting elements and photosensitive elements to efficiently transmitting the light signals from the light emitting elements through the optical fiber bundles to the photosensitive elements. Consequently, in the cause where the controlled circuit is made operative at high voltages, each optical fiber bundle may act as a leakage current path and relatively large leakage currents flow into the light emitting elements and this is the case that the light emitting elements are damaged. In a case where the controlled circuit is made operative at low voltages, since the optical fiber bundle serves as a good insulating material, the leakage currents flowing through the optical fiber bundles are small enough to be neglected, so that they will not break the light emitting elements. Therefore, conventionally, in the case where the controlled circuit is made operative at high voltages, it was thought that it is very difficult to utilize this kind of optically controlling technology.